(function (doc, win) {
    var docEl = doc.documentElement
    var resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize'
    var recalc = function () {
      var clientWidth = docEl.clientWidth
      if (!clientWidth) return
      docEl.style.fontSize = (clientWidth / 10) + 'px'
    }
   
    if (!doc.addEventListener) return
    win.addEventListener(resizeEvt, recalc, false)
    doc.addEventListener('DOMContentLoaded', recalc, false)
  })(document, window)
  